This and the following patches aim to optimize the code dealing with
page tables and TLB operations. Each patch reduces the time it takes
to gzip a 16 MB file slightly, but I expect things like fork() and
mmap() will improve somewhat more.

This patch deals with the low-level TLB operations:

  * Remove unused _TLBEHI_I define
  * Use gcc builtins instead of inline assembly
  * Remove a few unnecessary pipeline flushes and nops
  * Introduce NR_TLB_ENTRIES define and use it instead of hardcoding it
    to 32 a few places throughout the code.
  * Use sysreg bitops instead of hardcoded shifts and masks
  * Make a few needlessly global functions static
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>